This proposal is part of an application for a Minority School Faculty Development Award from the National Heart, Lung, and Blood Institute for Meharry Medical College. It is a proposal to investigate familial, nutritional, behavioral, and neurophysiological factors affecting cardiovascular function in blacks. Young black normotensive men equally divided by parental history of essential hypertension will be evaluated for cardiovascular reactivity during twelve days of controlled dietary intake. Blood pressures will be monitored while subjects consume either a high sodium-high calcium, high sodium-low calcium, low sodium-high calcium, or a low sodium-low calcium diet. Comparisons of blood pressures will be made between dietary conditions and to measurements obtained during a 12-day ad lib dietary period either four months before or four months after the dietary intervention. At the end of the dietary period, subjects will be evaluated for cardiovascular reactivity using a modified Stroop task to evaluate beta-adrenergic function, the Cold Face Stimulus test to evaluate alpha-adrenergic function, head-tilt test to study baroreceptor and parasympathetic neural tone, and microneurography to examine sympathetic nerve activity. Urinary chemistries will verify dietary compliance and permit analyses of nutritional influences on cardiovascular reactivity. All subjects will be pre-tested using a questionnaire with four measures of hostility from the Minnesota Multiphasic Personality Inventory. Preliminary investigations support the expectation that high dietary calcium will attenuate reactivity of the sympathetic nervous system and the reactivity of blood pressure to excessive sodium. It is also expected that subjects with positive parental histories of hypertension and/or high manifest hostility will reveal exaggerated reactivity to dietary, mental, and physical challenges with corresponding differentiations of autonomic functioning. These investigations are expected to provide significant new information about the disproportionate vulnerability of blacks to premature cardiovascular disease.